US4097071A - Flexible exhaust coupling - Google Patents

Abstract

An exhaust pipe of a front engine mounted transversely to roll about an axis transverse to the longitudinal axis of the vehicle is joined to a tailpipe by an improved high temperature resistant flexible coupling including a spherically surfaced ring seal supported between a tubular end segment of a first pipe and a free end spherical surface on a second pipe; the second pipe having a flange connected thereto and a pair of bolts are resiliently coupled to the flange fixed on the first pipe to bias the spherical lip against a high temperature lubricant surface on the seal to define a joint with minimal resistance to roll motion so that it readily accommodates substantial angular offset between the first and second pipe segments during high temperature exhaust conditions while maintaining a positively sealed surface at the joint.

Description

This invention relates to flexible couplings for connecting an exhaust pipe to a tailpipe and more particularly to flexible exhaust couplings for use with front engine driven vehicles having an engine mounted to roll about an axis transverse to the longitudinal axis of exhaust and tailpipe components of an automotive exhaust system.

Various proposals have been suggested to accommodate for engine roll in front mounted transverse engine applications wherein the engine rolls about an axis transverse to the longitudinal axis of an exhaust system which follows the longitudinal axis of a vehicle.

More particularly, in such arrangements, one proposal is to provide a bellows type connection between the exhaust pipe and downstream exhaust components. A flexible bellows component of the coupling is typically made of high cost temperature resistant alloy metal which contracts and expands in accordance with fore and aft engine roll to accommodate substantial angular movements produced between an exhaust pipe segment connected to the engine and a downstream exhaust pipe component connected by suitable flexible hangers to the vehicle frame.

Spherical type exhaust couplings are known such as in U.S. Pat. No. 3,188,115 issued June 8, 1965, to Morrish et al where an exhaust pipe is directly connected to the exhaust manifold by an external double spherical fitting configured to accommodate a slight angular offset between the exhaust pipe and the exhaust manifold. In such arrangements an outer spherical fitting component is spring biased against an intermediate spherical fitting to hold it on a spherical seat of the exhaust manifold. The double spherical fitting maintains a spring bias on a sealed joint between the exhaust manifold and the intermediate spherical fitting through wide temperature excursions without accommodating the constant roll movement of a transversely mounted engine as it is transmitted into a downstream, axially oriented exhaust system.

Other proposals with spherical surface on an exhaust pipe having inside and outside spherical surfaces in sandwiched relationship of limited roll freedom are set forth in U.S. Pat. No. 3,047,315 issued July 31, 1962, to Kinnison and U.S. Pat. No. 2,840,394 issued June 24, 1958, to Rohr. While all of the aforesaid coupling configurations are suitable to maintain a tightly sealed joint at exhaust manifolds and the like, they do not include provision for joint movements which will accommodate substantial angular movement between an exhaust pipe and downstream exhaust components as is found in a front located, transversely mounted engine and associated exhaust system.

Accordingly, an object of the present invention is to improve automotive exhaust systems for use with a front located transversely mounted engine by the provision therein of a low cost exhaust coupling having a flange fixedly secured to each of first and second pipes at points offset from free ends on each of the pipes and having an interposed seal element supported between the free ends and having a spherical seal surface impregnated with low friction, high temperature material to reduce frictional drag between it and a spherical joint surface on one of the free ends and wherein the flanges are interconnected by a pair of attachment bolts threaded to one flange and spring coupled to the other flange so that the spherical joint surface on one of the free ends will be continuously spring biased against the spherical seal surface and yet free to pivot with respect thereto while defining a continuous annular seal surface therebetween throughout substantial angular movements between the first and second pipes.

Still another object of the present invention is to provide a low cost, flexible exhaust coupling for use in engine exhaust systems wherein the engine is front located and transversely mounted to have a roll axle transverse to the longitudinal axis of the vehicle and wherein the exhaust system includes exhaust and tailpipe components arranged generally longitudinally of the vehicle by the provision of two pipes each having a flange fixedly connected thereon and each including a free end between each of the fixed flanges and telescoped with one another to have a space therebetween occupied by an annular seal element having a spherical end surface impregnated with a low friction, high temperature resistant material and in engagement with a spherical surface on one of the free ends and wherein each of the fixed flanges are spring biased by resilient means to accommodate substantial angular movement between the two pipes.

Yet another object of the present invention is to provide an exhaust coupling as set forth in the preceding object wherein the resilient means includes a pair of attachment bolts each threaded to one flange and oriented in the plane of the rocking motion of the engine and each coupled to the other flange by a conical spring grounded on the other of the flanges and to a shoulder on the attachment bolt to produce an axial spring bias of the one free end to the spherical end surface and a sealed interconnection between the pipes that permits a substantial angular movement between the pipes and wherein the pipes are easily moved at the coupling without binding therein.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

FIG. 1 is a diagrammatic view of an engine exhaust system including the present invention;

FIG. 2 is an enlarged vertical sectional view taken along theline 2--2 of FIG. 1; and

FIG 3 is a view in perspective showing the component parts of the invention in an exploded relationship.

In FIG. 1, a front located, transversely mountedengine 10 is illustrated having a roll axis 12 arranged generally transversely to thelongitudinal extent 14 of the vehicle.

The engine includesexhaust pipes 16, 18 joined at asingle outlet pipe 20 that is joined by acoupling 22, constructed in accordance with the present invention, to apipe 24 leading to a downstream, exhaust gas converter 26. Anoutlet pipe 28 from the converter 26 is connected by asecond coupling 30 to downstream exhaust components.

When an engine is supported transversely in a vehicle support system including resilient engine mounts, it basically rolls about an axis transverse to the longitudinal axis of downstream pipe components of an exhaust system associated with the engine. Furthermore, such engines are susceptible to vertical displacement and yaw movements that all combine to direct a substantial rolling movement between an exhaust pipe component leading to an exhaust system and the remainder of the downstream components in the exhaust system. In such arrangements the longitudinal extent of the exhaust system must withstand bending offset and thermal expansion forces thereon while retaining a gas tight seal between the interconnected components.

Each of theexhaust couplings 22, 30 are specifically configured to accommodate bending by rocking motion of the joint and to do so by means of a unique interconnection between first and second pipe components that enable the interconnected pipe components to be freely moved through substantial angular offsets without resistance to such movement of the pipe components and to do so while maintaining a tight gas seal at a sealed joint in the coupling.

More particularly, in the illustrated arrangement thecoupling 22 is detailedly set forth in FIGS. 2 and 3 with it being understood thatcoupling 30 is indentical.Coupling 22 has aseal flange 32 located in surrounding relationship to the outer periphery of theexhaust pipe 20 and upstream of afree end 34 onpipe 20.Free end 34 extends inboard of thecoupling 22 from theseal flange 32 and in telescoped relationship to afree end 35 onpipe 24. Theflange 32 is fixedly secured to theexhaust pipe 20 by acircumferential weldment 37 that securely fastens theseal flange 32 against movement with respect to theexhaust pipe 20. Weldment 37 is continuously circumferentially formed and is of a density to be gas tight thereby to seal theflange 32 to pipe 20.

The coupling further includes asecond flange 36 fixedly connected to a portion of thepipe 24 by acircumferential weldment 38 at a point spaced downstream offree end 35.Free end 35 is flared radially outwardly to form an inboardspherical seal surface 39 spaced radially of and extending circumferentially around the outer surface offree end 34.

Thespherical seal surface 39 is supportingly received on a spherical surface 40 on a ring seal element 42 that is located interiorly of thecoupling 22 to separate theflanges 32 and 36 from one another and to serve as a load transfer component between thefree end 34 and thefree end 35. More particularly, the ring seal 42 includes anaxial bore 44 therethrough in which the outer surface of thepipe end 34 is inserted to support the ring seal 42 radially outwardly thereof. The ring seal 42 further includes a radially outwardly directedseal surface 46 thereon that engages aninboard shoulder 48 on theflange 32 to define a sealed joint therebetween. In one working embodiment ring seal 42 is made of compressed sheets of graphite laminated to S.A.E. 1009 steel foil. The graphite has 80% minimum type GTC graphite part density of 2.6 g/cm³ + 10%.

The separated parts in FIG. 3 are joined together in the working embodiment by a pair ofbolts 50, 52. Thebolts 50, 52 are directed throughclearance holes 54, 56, respectively, formed on either side of afront wall 58 of theflange 36. Each of thebolts 50, 52 further includes a threadedend 60 that is threadebly received within a tappedopening 62 inear portions 64, 66 of theseal flange 32. Theseal flange 32 is coupled to thekey flange 36 bybolts 50, 52 and flexible spring coupling means in the form of aconical spring 68 supported in surrounding relationship to the bolt 50 and aconical spring 70 located in surrounding relationship to theattachment bolt 52. More particularly, each of thesprings 68, 70 has asmall diameter end 71 in engagement with ahead 72 on each of thebolts 50, 52. An oppositelarge diameter end 73 of eachspring 68, 70 is seated against theoutboard face 74 of thewall 58 as best seen in FIG. 2. In the illustrated application of FIG. 1,conical springs 68, 70 are offset on either side of thecoupling 22 and are located in the roll plane of theengine 10. Such an arrangement keeps a constant axial load on the sealed joint by forcing thespherical surface 39 against the spherical surface 40 of the ring seal 42. The axial load is maintained throughout angular offset movements between thepipe segments 20, 24 as produced during engine roll excursions. Thesprings 68, 70 are located at the base or large diameter end thereof by theinside diameter 74 of thekey flange 36 and at the top by the inside diameter of thebolt head 72 so that flexing in thesprings 68, 70 takes place between these two anchor points.

Thefree ends 34, 35 and ring seal 42 space theflanges 32, 36 apart andflange 36 is located in spaced relationship toend 35. Thus, pivotal movement ofsurface 39 on surface 40 is able to accommodate the roll movement ofengine 10. More specifically, such movement is transmitted through theengine 10 throughbolts 50, 52 andsprings 68, 70 to accommodate angular offset between thefree ends 34, 35.

The spherical surface 40 of the seal is preferably impregnated with a special low friction high temperature resistant lubricant such as graphite. Other low friction high temperature lubricants are equally suited for use in the present invention. The use of such lubricant is desired in order to assure reduced frictional resistance against the free rocking movement of thesurface 39 with respect to the surface 40.

The illustrated seal is self-lubricating and antioxidant and will withstand temperatures in excess of 1000° F. The especially configured coupling allows thejoint 22 to flex continually and yet maintain a complete circumferential seal between the annularspherical surface 39 on thefree end 35 with respect to the spherical surface 40 on the seal element 42. Radial seal along theseal flange 32 is maintained by the axial force component provided by theconical springs 68, 70 as they pull theseal flange 32 and thereference shoulder 48 thereon with respect to theradial seal surface 46 of the ring seal 42. Any tendency for leakage along the outer surface of thefree end 34 is sealed by the continuously formed gastight weldment 37 between the outboard face of theseal flange 24 and theexhaust pipe 20.

Another feature of the present invention is thatfree end 34 protects thebore 44 andend surface 76 of ring seal 42 by directing exhuast gas in a downstream direction intocavity 78 formed byfree end 35. This avoids direct impact of exhaust against surfaces ofring seal 35 and consequent erosion.

In the illustrated arrangement thecoupling 30 has the same configuration as thecoupling 22 and is included in the exhaust system to serve as an isolater against transmission of noise propagated in theengine 10 by vibration and exhaust gas flow therefrom before it enters themuffler 34 and downstream exhaust pipe segments connected thereto.

Working embodiments of the present invention have been endurance tested under lab conditions where the couplings maintained a gas tight seal following cycling in excess of one million cycles of plus and minus four degrees of movement between the longitudinal axes ofpipe segment 20 andpipe segment 24. Such angular excursion simulates the typical angular movement produced by front located transversely mounted engines having a mount system that causes the engine to roll about an axis transverse to that of the longitudinal axis of the exhaust system. Moreover, the seals maintain an integral gas tight connection under conditions where the test couplings are subjected to an external environment with a 5 percent (5%) salt solution and abrasive dust components and where a temperature in the order of 900° F is applied.

The design has been found to have inherent abilities to flex more readily than heretofore known separate pipe coupling components and has been found to be more durable than integral bellows type metal flexible couplings for joining first and second pipe components. The illustrated arrangement is much more flexible than joint configurations having spherical surfaces of the double seal surface configuration where the spherical surfaces are effectively clamped with respect to one another. Moreover, the specifically illustrated spring configuration is such that the spring forces for maintaining radial and spherical interfaces between the component parts of the arrangement offer minimum resistance to rocking motion of the joint thereby to accommodate the roll motion of typically front located transversely mounted engine configurations.

While the embodiments of the present invention, as herein disclosed, constitute a preferred form, it is to be understood that other forms might be adopted.

Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A flexible exhaust coupling assembly for maintaining a circumferential seal between pipe segments subject to angular movement therebetween during exhaust flow therethrough comprising: a first pipe, a seal flange supported on said first pipe, means for connecting said seal flange to said first pipe and forming a continuous circumferential gas tight seal between seal load flange and said first pipe, said first pipe having a tubular free end thereon extending axially beyond said seal flange, a second pipe having a flared free end formed continuously circumferentially therearound, said flared free end having a spherical seal surface thereon, a key flange on said second pipe at a point axially spaced from said flared free end to prevent outer radial binding of said free end, means for fixedly securing said key flange to said second pipe segment, a ring seal having an outer peripheral spherical surface thereon impregated with high temperature lubricant material in engagement with said spherical seal surface and freely movable with respect thereto, said ring seal including a radial reference surface sealingly engageable with said seal flange to be located thereby axially with respect to said first pipe, means for spring biasing said flared free end axially against said outer peripheral spherical surface, said last mentioned means including a pair of bolts each having a threaded end thereon engaged with said seal flange and each including a segment freely movable with respect to said key flange and including a heat portion axially spaced with respect to said key flange, compression spring means in engagement with said head and said key flange, said compression spring means being spaced with respect to said key flange to permit angular movement of said first pipe segment with respect to said second pipe segment, said compression spring means biasing said flared free end with respect to said spherical outer surface on said ring seal to maintain a continuous circumferential seal therearound throughout the range of angular movements between the first and second pipes.

2. A flexible exhaust coupling assembly for maintaining a circumferential seal between pipe segments subject to angular movement therebetween during exhaust flow therethrough comprising: a first pipe, a seal flange supported on said first pipe, means for connecting said seal flange to said first pipe and forming a continuous circumferential gas tight seal between seal load flange and said first pipe, said first pipe having a tubular free end thereon extending axially beyond said seal flange, a second pipe having a flared free end formed continuously circumferentially therearound, said flared free end having a spherical seal surface thereon, a key flange on said second pipe at a point axially spaced from said flared free end to prevent outer radial binding of said free end, means for fixedly securing said key flange to said second pipe segment, a ring seal having an outer peripheral surface thereon impregnated with high temperature lubricant material in engagement with said spherical surface and freely movable with respect thereto, said ring seal including a radial reference surface sealingly engageable with said seal flange to be located thereby axially with respect to said first pipe, means for spring biasing said flared free end axially against said spherical outer surface, said last mentioned means including a pair of bolts each having a threaded end thereon engaged with said seal flange and each including a segment freely movable with respect to said key flange and including a head portion axially spaced with respect to said key flange, coned spring elements having a small diameter end in engagement with said head and a large diameter end in engagement with said key flange, said coned spring elements each being spaced with respect to said key flange to permit angular movement of said first pipe segment with respect to said second pipe segment, said coned spring biasing said flared free end with respect to said outer peripheral spherical surface on said ring seal to maintain a continuous circumferential seal therearound throughout the range of angular movements between the first and second pipes.

3. A flexible exhaust coupling assembly for maintaining a circumferential seal between pipe segments subject to angular movement therebetween during exhaust flow therethrough comprising: a first pipe, a seal flange supported on said first pipe, means for connecting said seal flange to said first pipe and forming a continuous circumferential gas tight seal between seal load flange and said first pipe, said first pipe having a tubular free end thereon extending axially beyond said seal flange, a second pipe having a flared free end formed continuously circumferentially therearound, said flared free end having a spherical seal surface thereon, a key flange on said second pipe at a point axially spaced from said flared free end to prevent outer radial binding of said free end, means for fixedly securing said key flange to said second pipe segment, a ring seal having an outer peripheral spherical surface thereon impregnated with high temperature lubricant material in engagement with said spherical seal surface and freely movable with respect thereto, said ring seal having an inside bore therethrough receiving said tubular free end to overlie said ring seal for shielding said ring seal from exhaust erosion, said ring seal including a radial reference surface sealingly engageable with said seal flange to be located thereby axially with respect to said first pipe, means for spring biasing said flared free end axially against said outer peripheral spherical surface, said last mentioned means including a pair of bolts each having a threaded end thereon engaged with said seal flange and each including a segment freely movable with respect to said key flange and including a head portion axially spaced with respect to said key flange, compression spring means in engagement with said bolt and said key flange, said compression spring means being spaced with respect to said key flange to permit angular movement of said first pipe segment with respect to said second pipe segment, said compression spring means biasing said flared free end with respect to said outer peripheral spherical surface on said ring seal to maintain a continuous circumferential seal therearound throughout the range of angular movements between the first and second pipes.

4. A flexible exhaust coupling assembly for maintaining a circumferential seal between pipe segments subject to angular movement therebetween during exhaust flow therethrough comprising: a first pipe, a seal flange supported on said first pipe, means for connecting said seal flange to said first pipe and forming a continuous circumferential gas tight seal between seal load flange and said first pipe, said first pipe having a tubular free end thereon extending axially beyond said seal flange, a second pipe having a flared free end formed continuously circumferentially therearound, said flared free end having a spherical seal surface thereon, a key flange on said second pipe at a point axially spaced from said flared free end to prevent outer radial binding of said free end, means for fixedly securing said key flange to said second pipe segment, a ring seal having an outer peripheral spherical surface thereon impregnated with high temperature lubricant material in engagement with said spherical seal surface and freely movable with respect thereto, said ring seal having an inside bore therethrough receiving said tubular free end to overlie said ring seal for shielding said ring seal from exhaust erosion, said ring seal including a radial reference surface sealingly engageable with said seal flange to be located thereby axially with respect to said first pipe, means for spring biasing said flared free end axially against said spherical outer surface, said last mentioned means including a pair of bolts each having a threaded end thereon engaged with said seal flange and each including a segment freely movable with respect to said key flange and including a head portion axially spaced with respect to said key flange, coned spring elements having a small diameter end in engagement with said head and a large diameter end in engagement with said key flange, said coned spring elements each being spaced with respect to said key flange to permit angular movement of said first pipe segment with respect to said second pipe segment, said coned spring biasing said flared free end with respect to said outer peripheral spherical surface on said ring seal to maintain a continuous circumferential seal therearound throughout the range of angular movements between the first and second pipe segments.

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